With swift development of communications technologies, more and more wireless applications are developed to enrich people's life and communications. Available spectrum resources that support wireless communications, however, are limited. With the increase of wireless applications, shortage of radio spectrum resources becomes more and more serious. Therefore, a major challenge to wireless communications at present is to increase utilization efficiency of the radio spectrum.
At present, allocation of the radio spectrum follows a fixed allocation pattern in all countries, where the spectrum is divided to a plurality of spectrum bands that do not overlap with one another. A spectrum band that is allocated to a specific operator for operation of a specific wireless application is called a licensed band. A spectrum band that is not licensed to a specific operator and that can be used for communication by any device compliant with requirements defined by the Radio Regulatory Committee is called an unlicensed band.
At present, long-distance communications generally use licensed bands. A common practice is to adopt an architecture consisting essentially of system devices (such as a base station, a base station controller, and a core network), where communications between user equipments (such as a mobile phone) are all forwarded by the system devices. In communications using licensed bands, communication resources are scheduled by a network in a centralized manner, which guarantees communication quality, but generally requires a high communication cost. Short-range communications, however, mostly use unlicensed bands. For communications using unlicensed bands, collision detection and avoidance techniques are generally required. When a user is using an unlicensed band, it is necessary to first check whether the spectrum band is occupied or idle, because a spectrum band can be used only when it is idle. If it is detected that the spectrum band is occupied, another check will be performed after a random time interval. Data is not transmitted until an idle spectrum band is detected, and once a communication session is completed, the channel is released immediately. In this communication mode, in the case of a large number of users and a congested spectrum band, the waiting time will be long and therefore communication quality cannot be guaranteed. The communication cost, however, is low.
As wireless services develop quickly, more and more terminals integrate multiple communication protocols. For example, many terminals integrate Wideband Code Division Multiple Access (WCDMA) and wireless broadband access (wireless local area network (WLAN), also known as Wireless Fidelity (WiFi)) protocols. In WiFi-deployed hotspot areas, users access the Internet over WiFi. In non-WiFi-deployed areas or when voice communication is needed, users access the Internet or carry out voice communication over WCDMA. Due to their low prices, unlicensed bands are used by many users so that the spectrum bands are congested. When there are too many users, normal communication requirements cannot be satisfied. In the case of licensed bands, on the other hand, because the spectrum is exclusively occupied, when there are few users, a large amount of spectrum will be idle, which is a waste of precious spectrum resources.
To solve the problem, a mechanism called opportunistic spectrum access or cognitive radio (CR) is proposed in the prior art, where a user granted with the right to use a licensed band is called a licensed user and a user not granted with the right to use a licensed band is called an unlicensed user. In opportunistic spectrum access mode, unlicensed users may use idle spectrum resources that are not occupied by licensed users. Specifically, unlicensed users can detect idle spectrum resources that are not occupied by licensed users and the detected idle spectrum resources are utilized to complete wireless communications between unlicensed users. This technology allows use of idle licensed bands, which effectively promotes the utilization efficiency of the spectrum.
The inventor of the present invention, however, discovers that the prior art has at least the following defect: the current spectrum detection is generally conducted by using energy detection to perform spectrum scanning, and a spectrum band is considered idle if its energy is below a specific threshold, and as a result, on the one hand, an unlicensed user may fail to detect a communication of a distant licensed user and hence take a spectrum band as an idle spectrum band and use it, which consequently causes interference to the communication of the licensed user; and on the other hand, because the spectrum of licensed users changes dynamically, it is possible that a spectrum band is idle at the time of detection but a licensed user initiates a communication when an unlicensed user is using the spectrum band, in which case, the unlicensed user also causes interference to the licensed user.